Kobayashi Y, Ohshiro N, Suzuki M, Sasaki T, Tokuyama S, Yoshida T, Yamamoto T
Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Showa University, Tokyo, Japan.
J Toxicol Sci. 2000 Aug;25(3):213-22. doi: 10.2131/jts.25.3_213.
We examined the effect of hemin on rat hepatic microsomal cytochrome P450 (P450) and its molecular species (P450 2E1, 3A2, 2C11 and 2C12) under the induction of heme oxygenase activity in male and female rats. Hemin produced an inverse relationship between the induction of heme oxygenase activity and the decrease of P450 content in a dose-dependent manner. A time course study revealed that hemin produced a significant decrease in total P450 content in male rats to about 37% that of the controls at 24 hr after its administration. Western and Northern blot analyses revealed that the increase in both heme oxygenase-1 (HO-1) protein and HO-1 mRNA reached a maximum at 24 hr and returned to control levels within 120 hr in both sexes. With respect to P450-dependent monooxygenase activities, we found that there was a significant decrease of aniline p-hydroxylase activity to about 30% of the control animals, but not in erythromycin N-demethylase activity at various time intervals. Immunoblot analysis revealed that P450 2E1 in male rat liver was dramatically decreased at 24 hr to about 20% of the controls, but not P450 3A2. Parallel to the decrease of androstenedione 16 alpha-hydroxylase activity, there was a marked decrease of P450 2C11 or 2C12 in male or female rats, respectively, at 72 hr after the treatment; however, hemin did not decrease androstenedione 16 alpha-hydroxylase activity in phenobarbital-pretreated rat liver. These findings suggest that hemin predominantly affects constitutively expressed isozymes rather than inducible P450 species in rat liver.
我们研究了氯化血红素对雄性和雌性大鼠血红素加氧酶活性诱导下大鼠肝微粒体细胞色素P450（P450）及其分子亚型（P450 2E1、3A2、2C11和2C12）的影响。氯化血红素以剂量依赖的方式在血红素加氧酶活性诱导与P450含量降低之间产生了负相关关系。一项时间进程研究表明，氯化血红素给药后24小时，雄性大鼠总P450含量显著降低至对照组的约37%。蛋白质免疫印迹和RNA印迹分析表明，血红素加氧酶-1（HO-1）蛋白和HO-1 mRNA的增加在24小时达到最大值，并在120小时内恢复到两性的对照水平。关于P450依赖性单加氧酶活性，我们发现在不同时间间隔，苯胺对羟基化酶活性显著降低至对照动物的约30%，但红霉素N-脱甲基酶活性未降低。免疫印迹分析表明，雄性大鼠肝脏中的P450 2E1在24小时显著降低至对照组的约20%，但P450 3A2未降低。与雄烯二酮16α-羟化酶活性降低平行，治疗后72小时，雄性或雌性大鼠中P450 2C11或2C12分别显著降低；然而，氯化血红素并未降低苯巴比妥预处理大鼠肝脏中的雄烯二酮16α-羟化酶活性。这些发现表明，氯化血红素主要影响大鼠肝脏中组成型表达的同工酶，而非诱导型P450亚型。
